Day 21 test but my cycle is only 20 days long

My partner and I have been ttc for about 2 years, we are both 23. My cycles have always been all over the place, for a few months they were every two weeks, then roughly every 25-30 days for a few months then all over the place (minimum 17 days, maximum 36 days) for a few month and now they are nearly always 20 days long. I've tracked temp, mucus, cervix position etc etc all before and these have consistently shown that I have not been ovulating. I am seeing my doctor on Thursday about our fertility issues and I know that one of the tests that can/will be done is the day 21 test.

My question is, since my cycles are so short, when in my cycle will this test probably need to be done? I am on day 8 right now and finished AF 2 days ago.

It's called Day 21 test because for a perfect cycle, day 21 is 7 days after presumed ovulation, and it's the 7 days after that's the important bit with these blood tests. So I imagine they will ask you to try and test and work out your ovulation and book in for tests 7 days after that...

That's just a guess however, I have longer cycles so my Day 21 tests were actually on day 28!

When you see your GP though, he/she will probably help you work this out especially with such a short cycle.

Hi there. I'm sorry you're having to investigate infertility. It must be so hard when your cycles are so irratic! I used to have 21d cycles and they were lengthened via acupuncture. Chinese medicine is a lot more concerned with cycle length than western medicine - it's considered a lot more important to be 27-29 days. I would try that for sure. To answer your question though, it's roughly 75% of the way through your cycle, so day 16

Would refrain from temping, it did not work out last time and will not do so now. Don't waste your time or further time doing that.

Have you been referred as a couple to a subfertility unit?. I would ask them about them doing this now on Thursday.

You should be passed on now to the specialists because you first and foremost need a diagnosis of the underlying problem. Both you and your man need to be investigated further and your tests done in tandem.

If periods are irregular as well then blood tests can be infact done according to calendar days.

Irregular periods are often caused by underlying hormonal imbalances, in this respect a condition called polycystic ovaries is a common culprit. Given your long standing irregular cycles as well they should look for this now to see if it is present. One blood test that should already have been done is a day 2 test to check and compare your LH level against that of your FSH. These should be the same; an imbalance of LH to FSH may well be indicative of polycystic ovaries. All these tests going forward should now be done under the auspices of a hospital rather than a GP.

Thanks Attila, tomorrow will be the first time I've spoke to a doctor about our issues though so no tests have been carried out in the past. Our friends have just had their DS #2 and it's what is fueling us to get this all started, seeing him just broke my heart that we haven't even been close yet